Metal landing on top electrode of RRAM

ABSTRACT

Some embodiments relate to an integrated circuit including a memory cell. The integrated circuit includes a semiconductor substrate and an interconnect structure disposed over the semiconductor substrate. The interconnect structure includes a plurality of dielectric layers and a plurality of metal layers that are stacked over one another in alternating fashion. The plurality of metal layers include a lower metal layer and an upper metal layer disposed over the lower metal layer. A bottom electrode is disposed over and in electrical contact with the lower metal layer. A data storage layer is disposed over an upper surface of bottom electrode. A top electrode is disposed over an upper surface of the data storage layer and is in direct electrical contact with a lower surface of the upper metal layer.

BACKGROUND

Many modern day electronic devices contain electronic memory. Electronicmemory may be volatile memory or non-volatile memory. Non-volatilememory retains its stored data in the absence of power, whereas volatilememory loses its stored data when power is lost. Resistive random accessmemory (RRAM) is one promising candidate for next generationnon-volatile memory due to its simple structure and its compatibilitywith complementary metal-oxide-semiconductor (CMOS) logic fabricationprocesses.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of an RRAM cell in accordancewith some embodiments.

FIG. 2 illustrates a cross-sectional view of an RRAM cell in accordancewith other embodiments.

FIG. 3A illustrates a cross-sectional view of some embodiments of anintegrated circuit including RRAM cells arranged in an interconnectstructure.

FIG. 3B illustrates a top view of some embodiments of an integratedcircuit including RRAM cells in accordance with FIG. 3A.

FIG. 4 illustrates a flow chart depicting a method in accordance withsome embodiments

FIGS. 5 through 16 illustrate a series of incremental manufacturingsteps as a series of cross-sectional views.

FIG. 17 illustrates a flow chart depicting a method in accordance withsome embodiments

FIGS. 18 through 34 illustrate a series of incremental manufacturingsteps as a series of cross-sectional views.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A resistive random-access memory (RRAM) cell includes upper and lowerelectrodes, and a variable resistance element disposed between the upperand lower electrodes. The variable resistance element can be switchedbetween different resistances that correspond to different data states,thereby enabling the RRAM cell to store one or more bit of data. Inconventional RRAM cells, the upper electrode is coupled to an overlyingmetal layer (e.g., metal 1, metal 2, metal 3, etc.) by a contact or via.Although use of this coupling contact or via is widely adopted, theoverall height of this RRAM cell plus this contact or via thereover islarge relative to typical vertical spacing between adjacent metal layers(e.g., between a metal 2 layer and a metal 3 layer). To make this heightmore in line with the vertical spacing between adjacent metal layers,some embodiments of the present disclosure provides for techniques tocouple the top electrode directly to an overlying metal line without avia or contact there between.

Referring to FIG. 1, a cross-sectional view of an RRAM cell 100 inaccordance with some embodiments is provided. The RRAM cell 100 isdisposed between a lower metal layer 102 and an upper metal layer 104,and is surrounded by dielectric material 106 such as an inter-metaldielectric (IMD) layer or inter-layer dielectric (ILD) layer. In someembodiments, the upper and lower metal layers 102, 104 are made ofaluminum (Al), copper (Cu), tungsten (W), or combinations thereof, andthe dielectric material 106 is a low-κ or extreme low-κ (ELK) dielectricmaterial having a dielectric constant less than 3.9.

The RRAM cell 100 includes a bottom electrode 108 and a top electrode110, which are separated from one another by a variable resistanceelement 112. In some embodiments, the bottom electrode 108 and/or topelectrode 110 are made of platinum (Pt), aluminum copper (AlCu),titanium nitride (TiN), gold (Au), titanium (Ti), tantalum (Ta),tantalum nitride (TaN), tungsten (W), tungsten nitride (WN), or copper(Cu). In some embodiments, the bottom electrode 108 and top electrode110 can be made of the same material as one another; while in otherembodiments the bottom electrode 108 and top electrode 110 can be madeof different materials from one another.

The variable resistance element 112 can include a resistance switchinglayer 114 and a capping layer 116, which are stacked between the bottomand top electrodes 108, 110. In some embodiments, the resistanceswitching layer 114 is made of nickel oxide (NiO), titanium oxide (TiO),hafnium oxide (HfO), zirconium oxide (ZrO), zinc oxide (ZnO), tungstenoxide (WO₃), aluminum oxide (Al₂O₃), tantalum oxide (TaO), molybdenumoxide (MoO), or copper oxide (CuO), for example. In some embodiments,the capping layer 116 can be made of platinum (Pt), aluminum copper(AlCu), titanium nitride (TiN), gold (Au), titanium (Ti), tantalum (Ta),tantalum nitride (TaN), tungsten (W), tungsten nitride (WN), or copper(Cu); and can be made of the same material or different material fromthe bottom electrode 108 and/or top electrode 110.

An etch-stop layer 118 is arranged over the lower metal layer 102, and abase portion of the bottom electrode 108 extends downward through anopening in the etch stop layer 118 to contact to lower metal layer 102.The base portion, which has lower sidewalls separated by a firstdistance d1, is narrower than an upper portion of the bottom electrode,which has upper sidewalls separated by a second distance, d2. Adielectric liner 120 is conformally disposed over sidewalls of topelectrode 110, along sidewalls of capping layer 116, along sidewalls ofresistance switching layer 114, and along upper sidewalls of bottomelectrode 108. The dielectric liner 120 also extends laterally over theupper surface of etch-stop layer 118. In some embodiments, thedielectric liner 120 and etch stop layer 118 are made of silicon carbide(SiC), silicon dioxide (SiO₂), silicon oxynitride (SiON), or siliconnitride (Si₃N₄), and can be made of the same or different materials asone another.

Notably, the RRAM cell 100 has its top electrode 110 coupled directly toupper metal layer 104 without a via or contact there between. Topelectrode 110 has an upper planar surface which extends continuouslybetween sidewalls of the top electrode 110 and which directly abuts theupper metal layer 104, and which is co-planar with upper surfaces ofdielectric liner 120. Thus, the top electrode 110 can have a rectangularcross-section in some embodiments. Compared to conventional RRAM cellswhich have a via or contact coupling the top electrode to the overlyingmetal line, the RRAM cell 100 exhibits a diminished height which is morein line with the vertical spacing between other adjacent metal layers.This can allow for more streamlined integration, which can reduce costsand/or improve device reliability in some embodiments.

During operation of the RRAM cell 100, the resistance switching layer114 has a variable resistance that represents a unit of data, such as abit of data (or multiple bits of data), and the capping layer 116 isthought to transfer oxygen ions corresponding to oxygen vacancies to andfrom filaments in the resistance switching layer 114 to change theresistance of the resistance switching layer 114. Whether ions arestripped from the filaments within the resistance switching layer 114 orstuffed into the filaments of the resistance switching layer 114 dependson what bias is applied across the bottom and top electrodes 108, 110.For example, to write a first data state to the RRAM cell 100 (e.g., to“set” a logical “1”), a first bias can be applied across the bottom andtop electrodes 108, 110 to strip oxygen ions from filaments in theresistance switching layer 114 and move those ions to the capping layer116, thereby putting the resistance switching layer 114 in alow-resistance state. In contrast, to write a second data state to theRRAM cell 100 (e.g., “reset” a logical “0”), a second, different biascan be applied across the bottom and top electrodes 108, 110 to stuffoxygen ions from the capping layer 116 back into the filaments in theresistance switching layer 114, thereby putting the resistance switchinglayer 114 in a high-resistance state. Further, through application of athird bias condition (different from the first and second biasconditions) across the bottom and top electrodes 108, 110, theresistance of the resistance switching layer 114 can be measured todetermine the stored resistance (i.e., data state) in the RRAM cell 100.

FIG. 2 shows another embodiment of an RRAM cell 100B in accordance withother embodiments. Like FIG. 1's embodiment, the RRAM cell 100B includesa top electrode 110 having an upper surface that is in direct contactwith upper metal layer 104. Also like FIG. 1's embodiment, FIG. 2's topelectrode 110 has an upper planar surface which extends continuouslybetween sidewalls of the top electrode and which directly abuts theupper metal layer 104. RRAM cell 100B also RRAM sidewall spacers 122 a,122 b which abut outer sidewalls of top electrode 110 and capping layer116. The RRAM sidewall spacers 122 a, 122 b sit on outer edges of uppersurface of resistance switching layer 114, and can be made of adielectric material, such as silicon nitride (Si₃N₄), a multilayeroxide-nitride-oxide film, or un-doped silicate glass (USG), for example.The RRAM sidewall spacers 122 a, 122 b can have tapered or rounded uppersurfaces, and the dielectric liner 120 is disposed conformally over thestructure to follow outer sidewalls of the RRAM sidewall spacers 122 a,122 b, and extend downward along outer sidewalls of the resistanceswitching layer 114 and bottom electrode 108. Whereas FIG. 1's upperportion of bottom electrode 108 and top electrode 110 had equal widthsd₂; FIG. 2's bottom electrode 108 has a width d₂′ that is larger thanwidth d₃ of the top electrode 110.

FIG. 3A illustrates a cross sectional view of some embodiments of anintegrated circuit 300, which includes RRAM cells 302 a, 302 b disposedin an interconnect structure 304 of the integrated circuit 300. Theintegrated circuit 300 includes a substrate 306, which may be, forexample, a bulk substrate (e.g., a bulk silicon substrate) or asilicon-on-insulator (SOI) substrate, and is illustrated with one ormore shallow trench isolation (STI) regions 308.

Two word line transistors 310, 312 are disposed between the STI regions308. The word line transistors 310, 312 include word line gateelectrodes 314, 316, respectively; word line gate dielectrics 318, 320,respectively; word line sidewall spacers 322; and source/drain regions324. The source/drain regions 324 are disposed within the substrate 306between the word line gate electrodes 314, 316 and the STI regions 308,and are doped to have a first conductivity type which is opposite asecond conductivity type of a channel region under the gate dielectrics318, 320, respectively. The word line gate electrodes 314, 316 may be,for example, doped polysilicon or a metal, such as aluminum, copper, orcombinations thereof. The word line gate dielectrics 318, 320 may be,for example, an oxide, such as silicon dioxide, or a high-x dielectricmaterial. The word line sidewall spacers 322 can be made of siliconnitride (Si₃N₄), for example.

The interconnect structure 304 is arranged over the substrate 306 andcouples devices (e.g., transistors 310, 312) to one another. Theinterconnect structure 304 includes a plurality of IMD layers 326, 328,330, and a plurality of metallization layers 332, 334, 336 which arelayered over one another in alternating fashion. The IMD layers 326,328, 330 may be made of an oxide, such as silicon dioxide, or a low-κdielectric or an extreme low-κ dielectric. The metallization layers 332,334, 336 include metal lines 338, 340, 341, 342, which are formed withintrenches, and which may be made of a metal, such as copper, aluminum, orcombinations thereof. Contacts 344 extend from the bottom metallizationlayer 332 to the source/drain regions 324 and/or gate electrodes 314,316; and vias 346 extend between the metallization layers 332, 334. Thecontacts 344 and the vias 346 extend through dielectric-protectionlayers 350, 352, which can be made of dielectric material and can act asetch stop layers during manufacturing. The dielectric-protection layers350, 352 may be made of an extreme low-κ dielectric material, such asSiC, for example. The contacts 344 and the vias 346 may be made of ametal, such as copper, aluminum, tungsten, or combinations thereof, forexample.

RRAM cells 302 a, 302 b, which are configured to store respective datastates, are arranged within the interconnect structure 304 betweenneighboring metal layers. The RRAM cells 302 a, 302 b each include abottom electrode 354 and a top electrode 356, which are made ofconductive material. Between its top and bottom electrodes 354, 356,each RRAM cell 302 a, 302 b includes a variable resistance element 358,and a conformal dielectric layer 360 is disposed along sidewalls of theRRAM cells and over dielectric protection layer 352. The metal lines341, 342 each have a lowermost surface that is co-planar with and indirect electrical contact with (e.g., ohmically coupled to) a topsurface of top electrodes 356. These structures within RRAM cell 302 acan correspond to those previously described with regards to FIG. 1 orFIG. 2, and in which the top electrode 356 is in direct contact with theupper metal layer 341, 342.

Although FIG. 3A shows the RRAM cells 302 a, 302 b arranged between thesecond and third metal layers 334, 336, it will be appreciated that RRAMcells can be arranged between any neighboring metal layers in theinterconnect structure 304. Further, although FIG. 3 illustrates onlythree metal layers for purposes of illustration, any number of metallines can be included in interconnect structure 304. Further still, theRRAMs cells need not be arranged between the two uppermost metallizationlayers as illustrated, but additional dielectric-protection layers andmetallization layers can be included over the RRAM cells. Further,although this disclosure is described in the context of RRAM memorycells, it will be appreciated that these concepts can also be applied toother types of memory cells, such as ferromagnetic RAM (FeRAM) orphase-change RAM (PCRAM) for example, which are disposed betweenadjacent metallization layers, and can also be applied tometal-insulator-metal (MIM) capacitors. Accordingly, in thesealternative embodiments, a resistance switching layer (e.g., 112 in FIG.1 or 358 in FIG. 3) can more generally be referred to as a data storagelayer or a dielectric layer in the context of memory devices or MIMcapacitors.

FIG. 3B depicts some embodiments of a top view of FIG. 3A's integratedcircuit 300 as indicated in the cut-away lines shown in FIGS. 3A-3B. Ascan be seen, the RRAM cells 302 a, 302 b can have a square orrectangular shape when viewed from above in some embodiments. In otherembodiments, however, for example due to practicalities of many etchprocesses, the corners of the illustrated square shape can becomerounded, resulting in RRAM cells 302 a, 302 b having a square orrectangular shape with rounded corners, or having a circular or ovalshape when viewed from above. The MRAM cells 302 a, 302 b are arrangedunder metal lines 341, 342, respectively, and have top electrodes 356 indirect electrical connection with the metal lines 341, 342,respectively, without vias or contacts there between.

FIG. 4 provides a flowchart of some embodiments of a method 400 formanufacturing an RRAM cell in accordance with some embodiments. Whilethe disclosed method 400 and other methods that are illustrated and/ordescribed herein may be illustrated and/or described herein as a seriesof acts or events, it will be appreciated that the illustrated orderingof such acts or events are not to be interpreted in a limiting sense.For example, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. Further, not all illustrated acts may be required to implementone or more aspects or embodiments of the description herein, and one ormore of the acts depicted herein may be carried out in one or moreseparate acts and/or phases.

At 401, a substrate which includes RRAM top and bottom electrodes isprovided.

To form these RRAM top and bottom electrodes, a substrate is received at402. An interconnect structure, which includes a plurality of metallayers and dielectric layers stacked over one another over, is disposedover the substrate.

At 404, an etch stop layer is formed over an upper surface of a metallayer and over an upper surface of a dielectric layer of theinterconnect structure. A first mask is formed over the etch stop layer.

At 406, a first etch is performed with the first mask in place to forman opening in the etch stop layer.

At 408, a bottom electrode layer is formed to extend through the openingin the etch stop layer and make contact with the metal layer. Aresistance switching layer is formed over the bottom electrode layer, acapping layer is formed over resistance switching layer, and a topelectrode layer is formed over the capping layer. A second mask is thenformed and patterned over the top electrode layer.

At 410, a second etch is performed with the second mask in place topattern the top electrode and bottom electrode.

At 412, a conformal dielectric liner is formed over an upper surface andsidewalls of patterned top electrode. The conformal dielectric linerextends downward along sidewalls of the capping layer, resistanceswitching layer, and bottom electrode.

At 414, a bottom antireflective coating (BARC) layer and/or photoresistlayer are formed over the conformal dielectric liner.

At 416, a third etch is performed to etch back the BARC and/orphotoresist layer. This third etch removes a portion of the conformaldielectric liner to expose an upper surface of the patterned topelectrode while leaving a remaining portion of the conformal dielectricliner, BARC, and photoresist layer in place to cover sidewalls of thetop electrode and sidewalls of the bottom electrode.

At 418, a remainder of the BARC and photoresist layer is removed, forexample by ashing, thereby exposing upper and sidewall surfaces of theconformal dielectric liner.

At 420, an interlayer dielectric (ILD) layer is formed over the exposedupper surface of the patterned top electrode and over the upper surfacesand sidewalls of the conformal dielectric liner.

At 422, via openings and trench openings are formed in the ILD layer.

At 424, the via openings and trench openings are filled with metal toform conductive metal lines and conductive vias, where a metal line isin direct contact with the patterned top electrode.

With reference to FIGS. 5-16, a series of cross-sectional views thatcollectively illustrate an example manufacturing flow consistent withsome example of FIG. 4 is provided. Although FIGS. 5-16 are described inrelation to the method 400, it will be appreciated that the structuresdisclosed in FIGS. 5-16 are not limited to the method, but instead maystand alone as structures independent of the method. Similarly, althoughthe method is described in relation to FIGS. 5-16, it will beappreciated that the method is not limited to the structures disclosedin FIGS. 5-16, but instead may stand alone independent of the structuresdisclosed in FIGS. 5-16.

FIG. 5 illustrates a cross-sectional view of some embodimentscorresponding to Act 402 of FIG. 4.

FIG. 5 illustrates a cross-sectional view of some embodimentsillustrating an interconnect structure 304 disposed over a substrate306. The illustrated portion of the substrate includes a memory region502 and a logic region 504 surrounding the memory region 502. Theinterconnect structure 304 includes an IMD layer 328 and one or moremetal lines 340 which extend horizontally through the IMD layer 328.Other IMD layers and metal lines can also be included in interconnectstructure 304, but are omitted here for purposes of clarity. The IMDlayer 328 can be an oxide, such as silicon dioxide, a low-κ dielectricmaterial, or an extreme low-κ dielectric material. The metal line 340can be made of a metal, such as aluminum, copper, or combinationsthereof. In some embodiments, the substrate 306 can be a bulk siliconsubstrate or a semiconductor-on-insulator (SOI) substrate (e.g., siliconon insulator substrate). The substrate 306 can also be a binarysemiconductor substrate (e.g., GaAs), a tertiary semiconductor substrate(e.g., AlGaAs), or a higher order semiconductor substrate, for example.In many instances, the substrate 306 manifests as a semiconductor waferduring the method 400, and can have a diameter of 1-inch (25 mm); 2-inch(51 mm); 3-inch (76 mm); 4-inch (100 mm); 5-inch (130 mm) or 125 mm (4.9inch); 150 mm (5.9 inch, usually referred to as “6 inch”); 200 mm (7.9inch, usually referred to as “8 inch”); 300 mm (11.8 inch, usuallyreferred to as “12 inch”); or 450 mm (17.7 inch, usually referred to as“18 inch”); for example. After processing is completed, for exampleafter upper metal layer is formed over RRAM cells, such a wafer canoptionally be stacked with other wafers or die, and is then singulatedinto individual die which correspond to individual ICs.

FIG. 6 illustrates a cross-sectional view of some embodimentscorresponding to Act 404 of FIG. 4.

In FIG. 6, a dielectric-protection layer 352 is formed over IMD layer328 and over metal line 340. The dielectric-protection layer 352 is madeof dielectric material, such as an oxide or ELK dielectric, and acts asan etch-stop layer. In some embodiments, the dielectric-protection layer352 comprises SiC having a thickness of approximately 200 Angstroms. Amask 600, such as a hard mask, antireflective coating (ARC) layer,and/or photoresist layer, is then patterned over the dielectricprotection layer 352. Mask 600 can be formed, for example, by spinning alayer of photoresist onto the wafer, selectively exposing portions ofthe photoresist layer to light by shining light through a reticle, anddeveloping the exposed photoresist.

FIG. 7 illustrates a cross-sectional view of some embodimentscorresponding to Act 406 of FIG. 4.

In FIG. 7, a first etch 700 is carried out with the mask 600 in place toselectively remove portions of the dielectric-protection layer 352. InFIG. 7's embodiment, the first etch 700 is an anisotropic etch, such asa dry or plasma etch, that forms openings 702 having vertical sidewallsin the dielectric-protection layer 352. In other embodiments, anisotropic etch, such as a wet etch, can be used and the openings 702 canhave angled or tapered sidewalls that are non-vertical.

FIG. 8 illustrates a cross-sectional view of some embodimentscorresponding to Act 408 of FIG. 4.

In FIG. 8, a bottom electrode layer 354 is formed over thedielectric-protection layer 352, and extends downwardly through theopening in the dielectric-protection layer 352 to make electricalcontact with the metal line 340. A resistance switching layer 362 isthen formed over an upper surface of the bottom electrode layer 354, anda capping layer 364 is then formed over an upper surface of theresistance switching layer 362. A top electrode layer 356 is formed overthe capping layer 364. Further, the top electrode layer 356 may be, forexample, about 10-100 nanometers thick. A second mask 802 is disposedover an upper surface of the top electrode layer 356. In someembodiments, the second mask 802 is a photoresist mask, but can also bea hard mask such as a nitride mark.

FIG. 9 illustrates a cross-sectional view of some embodimentscorresponding to Act 410 of FIG. 4.

In FIG. 9, a second etch 902 is carried out with the second mask 802 inplace to selectively remove portions of the top electrode 356, cappinglayer 364, resistance switching layer 362, and bottom electrode 354until an upper surface of dielectric protection layer 352 is exposed. Insome embodiments, this second etch 902 is an anisotropic etch, such as aunidirectional or vertical etch.

FIG. 10 illustrates a cross-sectional view of some embodimentscorresponding to Act 412 of FIG. 4.

In FIG. 10, a conformal dielectric layer 1002 is formed over thestructure, lining the upper surface and sidewalls of the second mask802, sidewalls of the top electrode 356, sidewalls of the capping layer364, sidewalls of the resistance switching layer 362, and uppersidewalls of the bottom electrode 354. The conformal dielectric layer1002 may be formed of, for example, silicon nitride, silicon carbide, ora combination of one or more of the foregoing. The conformal dielectriclayer 1002 may be formed with a thickness of, for example, about 500Angstroms.

FIG. 11 illustrates a cross-sectional view of some embodimentscorresponding to Act 414 of FIG. 4.

In FIG. 11, a protective layer 1100 is formed over the structure. Insome embodiments, the protective layer 1100 is a BARC layer and/or aphotoresist layer.

FIG. 12 illustrates a cross-sectional view of some embodimentscorresponding to Act 416 of FIG. 4.

In FIG. 12, the protective layer 1100 has been etched back so as toremove the second mask layer 802 and portions of the conformaldielectric liner 1002, and thereby expose an upper surface of the topelectrode 356. Remaining portions of the protective layer 1100′ are leftin place to cover sidewalls of the conformal dielectric layer 1002 andextend laterally over upper surface of conformal dielectric layer 1002.

FIG. 13 illustrates a cross-sectional view of some embodimentscorresponding to Act 418 of FIG. 4.

In FIG. 13, remaining portions of the protective layer 1100′ have beenremoved. This removal may be accomplished, for example, by carrying outan ashing process 1300, such as a plasma ashing process.

FIG. 14 illustrates a cross-sectional view of some embodimentscorresponding to Act 420 of FIG. 4.

In FIG. 14, an IMD layer 1400, such as an extreme low-k dielectric layeris formed over the structure.

FIG. 15 illustrates a cross-sectional view of some embodimentscorresponding to Act 422 of FIG. 4.

In FIG. 15, photolithography is carried out to pattern one or more masks(not shown), and one or more corresponding etches are carried out toform trench openings 1500 and via openings 1502. In some embodiments,these openings can be dual-damascene openings. In FIG. 15, the viaopening 1502 is formed in the logic region and extends downward to anupper surface of lower metallization line 340.

FIG. 16 illustrates a cross-sectional view of some embodimentscorresponding to Act 424 of FIG. 4.

In FIG. 16, an upper metal layer 341, 342, 1600 is filled in the trenchopenings 1500 and via opening 1502. Thus, the upper metal layer 341, 342can be in direct contact with the upper surface of the top electrodes356 without a via connecting the top electrodes to the upper metallayer. For example, formation of the upper metal layer 341, 342, 1600may include upper depositing a barrier layer in the via and trenchopenings, forming a Cu seed layer over the barrier layer in the via andtrench openings, and then electroplating copper using the seed layer tofill the via and trench openings. Thus, the via openings and trenchopenings can be filled concurrently in some embodiments. After the uppermetal layer is formed, chemical mechanical planarization (CMP) may beused to planarize upper surfaces of upper metal layer and IMD layer1400.

FIG. 17 provides a flowchart of some other embodiments of a method 1700for manufacturing an RRAM cell in accordance with some embodiments.

At 1701, a substrate which includes RRAM top and bottom electrodes isprovided. To from these structures, at 1702, substrate is received. Thesubstrate includes an interconnect structure including a plurality ofmetal layers and dielectric layers stacked over one another over thesubstrate.

At 1704, an etch stop layer is formed over an upper surface of a metallayer and over an upper surface of a dielectric layer of theinterconnect structure. A first mask is formed over the etch stop layer.

At 1706, a first etch is performed with the first mask in place topattern the etch stop layer.

At 1708, a bottom electrode layer is formed over the etch stop layer,and a resistance switching layer is formed over the bottom electrodelayer. A capping layer is formed over resistance switching layer, and atop electrode layer is formed over the capping layer. A second mask isformed and patterned over the top electrode layer.

At 1710, a second etch is performed with the second mask in place topattern the top electrode and the capping layer.

At 1712, a conformal dielectric spacer layer is formed over an uppersurface and sidewalls of the patterned top electrode. The conformaldielectric spacer extends downward along sidewalls of capping layer, andcan also extend laterally over an upper surface of the resistanceswitching layer.

At 1714, the conformal dielectric spacer layer is etched back to formRRAM sidewall spacers, which are disposed about sidewalls of thepatterned top electrode and capping layer.

At 1716, a third mask is formed over the top electrodes, and a thirdetch is performed with the third mask in place to remove an exposedportion of the resistance switching layer and the bottom electrode.

At 1718, a conformal dielectric layer is formed over the structure. Theconformal dielectric layer extends over an upper surface and sidewallsof the patterned top electrode, sidewalls of the capping layer,sidewalls of the resistance switching layer, and sidewalls of the bottomelectrode.

At 1720, a BARC and/or photoresist coating is formed over the structure,and the BARC and/or photoresist is then etched back to remove theconformal dielectric layer over the top electrode, thereby exposing anupper surface of the top electrode. Remaining portions of the BARCand/or photoresist coating still cover sidewalls of the conformaldielectric layer.

At 1722, the remaining portions of the BARC and/or photoresist layer areremoved, thereby exposing sidewalls of the conformal dielectric liner.

At 1724, an ILD layer is formed over the exposed upper surface ofpatterned top electrode and over the conformal dielectric liner. In someembodiments, the ILD layer is made of an ELK dielectric material.

At 1726, via openings and trench openings are formed in the ILD layer.

At 1728, the via openings and trench openings are filled with metal toform conductive metal lines and conductive vias, where a metal line isin direct contact with the patterned top electrode.

With reference to FIGS. 18-34, a series of cross-sectional views thatcollectively illustrate an example manufacturing flow consistent withsome example of FIG. 17 is provided.

FIG. 18 illustrates a cross-sectional view of some embodimentscorresponding to Act 1702 of FIG. 17.

FIG. 18 illustrates a cross-sectional view of some embodimentsillustrating an interconnect structure 304 disposed over a substrate306. FIG. 5 illustrates a cross-sectional view of some embodimentsillustrating an interconnect structure 304 disposed over a substrate306, and can be the same as previously described with respect to FIG. 5.The illustrated portion of the substrate includes a memory region 502and a logic region 504 surrounding the memory region 502. Theinterconnect structure 304 includes an IMD layer 328 and one or moremetal lines 340 which extend horizontally through the IMD layer 328.

FIG. 19 illustrates a cross-sectional view of some embodimentscorresponding to Act 1704 of FIG. 17.

In FIG. 19, a dielectric-protection layer 352 is formed over IMD layer328 and over metal line 338. The dielectric-protection layer 352 is madeof dielectric material, such as an oxide or ELK dielectric, and acts asan etch-stop layer. In some embodiments, the dielectric-protection layer352 comprises SiC having a thickness of approximately 200 Angstroms. Amask 1900, such as a hard mask, antireflective coating (ARC) layer,and/or photoresist layer, is then patterned over the dielectricprotection layer 352.

FIG. 20 illustrates a cross-sectional view of some embodimentscorresponding to Act 1706 of FIG. 17.

In FIG. 20, a first etch 2000 is carried out with the mask 1900 in placeto selectively remove portions of the dielectric-protection layer 352.In FIG. 20's embodiment, the first etch is an isotropic etch, such as awet etch, that forms openings 2002 having rounded or tapered sidewallsin the dielectric-protection layer 352. In other embodiments, ananisotropic etch, such as a dry etch or plasma etch, can be used and mayform the openings with vertical sidewalls.

FIG. 21 illustrates a cross-sectional view of some embodimentscorresponding to Act 1708 of FIG. 4.

In FIG. 21, a bottom electrode layer 354 is formed over thedielectric-protection layer 352, and extends downwardly through theopening in the dielectric-protection layer 352 to make electricalcontact with the metal line 340. A resistance switching layer 362 isthen formed over an upper surface of the bottom electrode layer 354, anda capping layer 364 is then formed over an upper surface of theresistance switching layer 362. A top electrode layer 356 is formed overthe capping layer 364. Further, the top electrode layer 356 may be, forexample, about 10-100 nanometers thick. A second mask 2100 is disposedover an upper surface of the top electrode layer 356. In someembodiments, the second mask 2100 is a photoresist mask, but can also bea hard mask such as a nitride mark.

FIG. 22 illustrates a cross-sectional view of some embodimentscorresponding to Act 1710 of FIG. 4.

In FIG. 22, a second etch 2200 is carried out with the second mask 2100in place to selectively remove portions of the top electrode 356 andcapping layer 364 until an upper surface of resistance switching layeris exposed. In some embodiments, the second etch is an anisotropic etch,such as a unidirectional or vertical etch. The second mask 2100 canoptionally be removed after the second etch 2200.

FIG. 23 illustrates a cross-sectional view of some embodimentscorresponding to Act 1712 of FIG. 17.

In FIG. 23, a conformal dielectric spacer layer 2300 is formed over thestructure, lining the upper surface and sidewalls of the top electrode356, along sidewalls of the capping layer 364, and extending over anupper surface of resistance switching layer 362. The conformaldielectric spacer layer 2300 may be formed of, for example, siliconnitride, silicon carbide, or a combination of one or more of theforegoing. Even more, the conformal dielectric spacer layer may beformed with a thickness of, for example, about 500 Angstroms.

FIG. 24 illustrates a cross-sectional view of some embodimentscorresponding to Act 1714 of FIG. 17.

In FIG. 24, an etch back process 2400 is used to etch back the conformaldielectric spacer layer 2300 to form RRAM sidewall spacers 122.

FIG. 25 illustrates a cross-sectional view of some embodimentscorresponding to Act 1716 of FIG. 17.

In FIG. 25, a third mask 2500 is formed over the top electrode 356. Thethird mask can be a hard mask or a photomask, for example. Third Mask2500 can be formed, for example, by spinning a layer of photoresist ontothe wafer, selectively exposing portions of the photoresist layer tolight by shining light through a reticle, and developing the exposedphotoresist.

FIG. 26 illustrates a cross-sectional view of some embodimentscorresponding to Act 1716 of FIG. 17.

In FIG. 26, a third etch 2600 is carried out with the third mask 2500 inplace to remove exposed portions of the resistance switching layer 362and bottom electrode 354. In FIG. 27 the third mask 2500 has beenremoved, for example through a plasma etching process.

FIG. 28 illustrates a cross-sectional view of some embodimentscorresponding to Act 1718 of FIG. 17.

In FIG. 28, a conformal dielectric layer 2800 is formed over thestructure. The conformal dielectric layer 2800 may be formed of, forexample, silicon nitride, silicon carbide, or a combination of one ormore of the foregoing. The conformal dielectric layer 2800 may be formedwith a thickness of, for example, about 500 Angstroms.

FIG. 29 illustrates a cross-sectional view of some embodimentscorresponding to Act 1720 of FIG. 17.

In FIG. 29, a BARC layer 2900 and/or photoresist coating are formed overthe structure.

FIG. 30 illustrates a cross-sectional view of some embodimentscorresponding to Act 1720 of FIG. 17.

In FIG. 30, the BARC layer 2900 and/or photoresist coating is etchedback. This etch back removes a portion of the conformal dielectric layer2800 from over the upper surface of top electrode 356, and leavesremaining portions of conformal dielectric layer 2800 along sidewalls ofthe RRAM sidewall spacers 122, and along sidewalls of bottom electrode354. In FIG. 30, another mask and etch (not shown) have been used toremove the conformal dielectric layer 2800 from over the logic region504.

FIG. 31 illustrates a cross-sectional view of some embodimentscorresponding to Act 1722 of FIG. 17.

In FIG. 31, an in-situ ashing process 3100 is carried out to remove theremaining portions of the conformal dielectric layer 2800.

FIG. 32 illustrates a cross-sectional view of some embodimentscorresponding to Act 1724 of FIG. 17.

In FIG. 32, an IMD layer 3200, such as an extreme low-k dielectric layeris formed over the structure.

FIG. 33 illustrates a cross-sectional view of some embodimentscorresponding to Act 1726 of FIG. 17.

In FIG. 33, photolithography is carried out to pattern one or more masks(not shown), and one or more corresponding etches are carried out toform trench openings 3300 and via openings 3302. In some embodiments,these openings can be dual-damascene openings. In FIG. 33, the viaopening 3302 is formed in the logic region and extends downward to anupper surface of lower metallization line 340.

FIG. 34 illustrates a cross-sectional view of some embodimentscorresponding to Act 1728 of FIG. 17.

In FIG. 34, an upper metal layer 341, 342, 3400 is filled in the trenchopenings 3300 and via opening 3302. Thus, the upper metal layer 341, 342can be in direct contact with the upper surface of the top electrodes356 without a via connecting the top electrodes to the upper metallayer. For example, formation of the upper metal layer 341, 342, 3400may include upper depositing a barrier layer in the via and trenchopenings, forming a Cu seed layer over the barrier layer in the via andtrench openings, and then electroplating copper using the seed layer tofill the via and trench openings. After the upper metal layer is formed,chemical mechanical planarization (CMP) may be used to planarize uppersurfaces of upper metal layer and IMD layer 3200.

It will be appreciated that in this written description, as well as inthe claims below, the terms “first”, “second”, “second”, “third” etc.are merely generic identifiers used for ease of description todistinguish between different elements of a figure or a series offigures. In and of themselves, these terms do not imply any temporalordering or structural proximity for these elements, and are notintended to be descriptive of corresponding elements in differentillustrated embodiments and/or un-illustrated embodiments. For example,“a first dielectric layer” described in connection with a first figuremay not necessarily correspond to a “first dielectric layer” describedin connection with another figure, and may not necessarily correspond toa “first dielectric layer” in an un-illustrated embodiment.

Some embodiments relate to an integrated circuit including one or morememory cells arranged between an upper metal interconnect layer and alower metal interconnect layer. A memory cell includes a bottomelectrode coupled to the lower metal interconnect layer, a data storagelayer disposed over the bottom electrode, and a capping layer disposedover the resistance switching layer. A top electrode is disposed overthe capping layer. An upper surface of the top electrode is in directcontact with the upper metal interconnect layer without a via or contactcoupling the upper surface of the top electrode to the upper metalinterconnect layer.

Other embodiments relate to an integrated circuit (IC). The IC includesa semiconductor substrate including a memory region and a logic region.An interconnect structure is disposed over the memory region and thelogic region. The interconnect structure includes a plurality of metalinterconnect layers disposed over one another and isolated from oneanother by interlayer dielectric (ILD) material. A plurality of memorycells or MIM capacitors are arranged over the memory region and arearranged between a lower metal interconnect layer and an upper metalinterconnect layer adjacent to the lower metal interconnect layer. Amemory cell or MIM capacitor includes a bottom electrode coupled to anupper portion of the lower metal interconnect layer. The memory cell orMIM capacitor also includes a top electrode having an upper planarsurface which extends continuously between sidewalls of the topelectrode and which directly abuts a bottom surface of the upper metalinterconnect layer.

Still other embodiments relate to a method. In the method, asemiconductor substrate is received which has an interconnect structuredisposed over the substrate. A bottom electrode and a top electrode areformed over the interconnect structure over the memory region. Thebottom electrode is coupled to a lower metal layer in the interconnectstructure. The bottom and top electrodes are separated from one anotherby a data storage or dielectric layer. An interlayer dielectric (ILD)layer is formed over the top electrode. A trench opening having verticalor substantially vertical sidewalls is formed in the ILD layer. Thetrench opening exposes an upper surface of the top electrode. An uppermetal layer is formed in the trench opening. The upper metal layer is indirect contact with the top electrode.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit (IC) including one or morememory cells arranged between an upper metal interconnect layer and alower metal interconnect layer, a memory cell comprising: a bottomelectrode coupled to the lower metal interconnect layer; a data storageor dielectric layer disposed over the bottom electrode; a capping layerdisposed over the data storage or dielectric layer; a top electrodedisposed over the capping layer, wherein an upper surface of the topelectrode is in direct contact with the upper metal interconnect layerwithout a via or contact coupling the upper surface of the top electrodeto the upper metal interconnect layer; and sidewall spacers arrangedalong sidewalls of the top electrode and along sidewalls of the cappinglayer, and having bottom surfaces that rest on an upper surface of thedata storage or dielectric layer.
 2. The IC of claim 1, wherein the topelectrode has an upper planar surface which extends continuously betweensidewalls of the top electrode and which directly abuts the upper metalinterconnect layer.
 3. The IC of claim 2, wherein the bottom electrodehas a bottom electrode width and the top electrode has a top electrodewidth that is smaller than the bottom electrode width.
 4. The IC ofclaim 1, the memory cell further comprising: a conformal dielectriclayer extending along the sidewalls of the top electrode, extendingdownwardly along the sidewalls of the capping layer, along sidewalls ofthe data storage or dielectric layer, and along upper sidewalls of thebottom electrode.
 5. The IC of claim 1, further comprising: a conformaldielectric along outer sidewalls of the sidewall spacers and extendingdownward along outer sidewalls of the data storage or dielectric layerand bottom electrode.
 6. The IC of claim 5, wherein the data storage ordielectric layer is made of nickel oxide (NiO), titanium oxide (TiO),hafnium oxide (HfO), zirconium oxide (ZrO), zinc oxide (ZnO), tungstenoxide (WO₃), aluminum oxide (Al₂O₃), tantalum oxide (TaO), molybdenumoxide (MoO), or copper oxide (CuO).
 7. The IC of claim 5, wherein thetop and bottom electrodes are made of platinum, aluminum copper,titanium nitride, gold, titanium, tantalum, tantalum nitride, tungsten,tungsten nitride, or copper.
 8. The IC of claim 1, wherein the topelectrode includes a planar top surface and wherein the sidewall spacerseach include a planar top surface, the planar top surfaces of thesidewall spacers being co-planar with the planar top surface of the topelectrode.
 9. The IC of claim 8, wherein the sidewall spacers havetapered or rounded upper surfaces that extend upwardly from outermostsidewalls of the sidewall spacers to the planar top surfaces of thesidewall spacers.
 10. An integrated circuit (IC), comprising: asemiconductor substrate including a memory region and a logic region; aninterconnect structure disposed over the memory region and the logicregion, the interconnect structure including a plurality of metalinterconnect layers disposed over one another and isolated from oneanother by interlayer dielectric (ILD) material; and a plurality ofmemory cells or metal-insulator-metal (MIM) capacitors arranged over thememory region and arranged between a lower metal interconnect layer andan upper metal interconnect layer adjacent to the lower metalinterconnect layer, a memory cell or MIM capacitor including: a bottomelectrode coupled to an upper portion of the lower metal interconnectlayer, a top electrode having an upper planar surface which extendscontinuously between sidewalls of the top electrode and which directlyabuts a bottom surface of the upper metal interconnect layer without avia or contact coupling the upper surface of the top electrode to theupper metal interconnect layer, and a data storage or dielectric layerseparating the bottom electrode from the top electrode, wherein sidewallspacers are arranged along sidewalls of top electrode and have bottomsurfaces that rest on an upper surface of the data storage or dielectriclayer.
 11. The IC of claim 10, wherein the top electrode has an upperplanar surface which extends continuously between sidewalls of the topelectrode and which directly abuts a corresponding co-planar surface ofthe upper metal interconnect layer.
 12. The IC of claim 10, wherein theupper and lower metal interconnect layers are made of aluminum, copper,or an aluminum copper alloy; and wherein the ILD material has adielectric constant that is less than that of silicon dioxide.
 13. TheIC of claim 10, the memory cell or MIM capacitor further comprising: acapping layer made of different material than the data storage ordielectric layer, the capping layer and the data storage or dielectriclayer disposed between the top electrode and bottom electrode.
 14. TheIC of claim 13: wherein the top and bottom electrodes are made ofplatinum, aluminum copper, titanium nitride, gold, titanium, tantalum,tantalum nitride, tungsten, tungsten nitride, or copper; and wherein thedata storage or dielectric layer is made of nickel oxide (NiO), titaniumoxide (TiO), hafnium oxide (HfO), zirconium oxide (ZrO), zinc oxide(ZnO), tungsten oxide (WO₃), aluminum oxide (Al₂O₃), tantalum oxide(TaO), molybdenum oxide (MoO), or copper oxide (CuO).
 15. The IC ofclaim 10, wherein the bottom electrode has sidewalls which are spacedapart by a first distance, which is larger than a second distance atwhich sidewalls of the top electrode are spaced.
 16. The IC of claim 10,wherein the sidewall spacers each include a planar top surface, theplanar top surfaces of the sidewall spacers being co-planar with theplanar top surface of the top electrode.
 17. The IC of claim 16, whereinthe sidewall spacers have tapered or rounded upper surfaces that extendupwardly from outermost sidewalls of the sidewall spacers to the planartop surfaces of the sidewall spacers.
 18. The IC of claim 10, whereinthe top electrode includes a planar top surface and wherein the sidewallspacers each include a planar top surface, the planar top surfaces ofthe sidewall spacers being co-planar with the planar top surface of thetop electrode.
 19. An integrated circuit (IC) comprising: one or morememory cells arranged between an upper metal interconnect layer and alower metal interconnect layer, wherein a memory cell comprises: abottom electrode coupled to the lower metal interconnect layer, thebottom electrode comprising platinum, aluminum copper, titanium nitride,gold, titanium, tantalum, tantalum nitride, tungsten, tungsten nitride,or copper; a data storage layer disposed over the bottom electrode, thedata storage layer comprising nickel oxide (NiO), titanium oxide (TiO),hafnium oxide (HfO), zirconium oxide (ZrO), zinc oxide (ZnO), tungstenoxide (WO₃), aluminum oxide (Al₂O₃), tantalum oxide (TaO), molybdenumoxide (MoO), or copper oxide (CuO); and a top electrode disposed overthe data storage layer, the top electrode comprising platinum, aluminumcopper, titanium nitride, gold, titanium, tantalum, tantalum nitride,tungsten, tungsten nitride, or copper; and sidewall spacers arrangedalong sidewalls of the top electrode and having bottom surfaces thatrest on an upper surface of the data storage layer; wherein an uppersurface of the top electrode is in direct contact with the upper metalinterconnect layer without a via or contact coupling the upper surfaceof the top electrode to the upper metal interconnect layer.
 20. The ICof claim 19: wherein the top electrode includes a planar top surface andwherein the sidewall spacers each include a planar top surface, theplanar top surfaces of the sidewall spacers being co-planar with theplanar top surface of the top electrode; wherein the sidewall spacershave tapered or rounded upper surfaces that extend upwardly fromoutermost sidewalls of the sidewall spacers to the planar top surfacesof the sidewall spacers.